nfsd: New helper nfsd4_cb_sequence_done() for processing more cb errors

According to Christoph's advice, this patch introduce a new helper
nfsd4_cb_sequence_done() for processing more callback errors, following
the example of the client's nfs41_sequence_done().

Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index 4874ce5..583ffc1 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -67,8 +67,8 @@
 	struct rpc_message cb_msg;
 	struct nfsd4_callback_ops *cb_ops;
 	struct work_struct cb_work;
+	int cb_seq_status;
 	int cb_status;
-	bool cb_update_seq_nr;
 	bool cb_need_restart;
 };